Oxide magnets

ABSTRACT

AN OXIDE MAGNET CONSISTING PRIMARILY OF BAO AND FE2O3, THE MOLAR RATIO FO BAO TO FE2O3 BEIN BETWEEN 1:5 AND 1:6, AND CONTAINING IN ADDITON 0.05 TO 0.3% BY WEIGHT CAO AND 0.4 TO 0.65% BY WEIGHT OF SIO2, HAS LARGE COERCIVE FORCE AND HIGH MAGNETIC ENERGY.

Jan. 25, 1972 TERUHIKO OJIMA ETAL OXIDE MAGNETS Filed Sept. 4, 1969 G uss) Hc(oe) -2ooo y T; 12ooc (Bmmax 6 Sheets-Sheet l (Bl'Dmax X 10 Jan. 25, 1972 TERUl-"Ko )JlMA ETAL 3,637,605

OXIDE MAGNETS Filud Sept. 1, i969 6 Sheets-Sheet z T2= I200 C Cu0w1% M01012 0.35 0.5 0515 L0 0.05

Jan. 25, 1972 TERUH|KO OJIMA ETAL 3,637,605

OXIDE MAGNETS Filed Sept. 4., i969 6 Sheets-Sheet 5 Br(Gouss) Hc(0e) Fig 3000-2509 T2= I200 C SiO2wt% 6 0 2 0 4 07 lb 20 Jan. 25, 1972 TERUHlKQ QJIMA ET AL 3,637,605

OXIDE MAGNETS F'Llml Sept. -1, L969 6 Sheets-Sheet 4 6 (BH) 1O Br(GausS) Hc(Oe) ma)? Jan. 25, 1972 Filed Sept. 4.

lobo

Fig. 5

TERUHIKO OJIMA E OXIDE MAGNETS 6 Sheets-Sheet 5 510 5:3 sis FezOa/ 800 Jan. 25, 1972 TERUHlKO OJIMA ET AL 3,637,605

' OXIDE MAGNETS Filed Sept. 4. 1969 6 Sheets-Sheet 6 aHe Fig 6 FezOs/BaO "United States Patent Int. (:1. H011 1/00 US. Cl. 25262.59 1 Claim ABSTRACT OF THE DISCLOSURE An oxide magnet consisting primarily of BaO and Fe 0 the molar ratio of BaO to Fe O being between 1:5 and 1:6, and containing in addition 0.05 to 0.3% by weight CaO and 0.4 to 0.65% by weight of SiO,,, has large coercive force and high magnetic energy.

This invention relates to improvements in oxide magnet materials, particularly to improvements in oxide magnet materials having magnetoplumbite crystal structure composed of Mo.6Fe O where M is a metal selected from the group consisting of Ba, Sr and Pb.

It is well-known that the oxide magnet composed of BaO6FeO has good magnetic properties, that is, its coercive force B is large and its magnetic energy (BH) is higher than that of the cobalt ferrite magnet. The magnetic remanence tBr of BaO6Fe O is however, not satisfactorily large, and though various improvements were proposed, this defect has not been overcome.

It is, therefore, the object of this invention to improve the magnetic properties of the binary system comprising MO and Fe O More fully speaking, the object of this invention is to improve Br, 13 and (B'Hh of the magnet of above-mentioned binary system, where the molar ratio of Fe O to M0 is between to 6, by adding small quantities of CaO and SiO This invention may be more readily understood by reference to the following detailed description and to the accompanying drawings, in which:

FIGS. 1 and 4 show curves indicating magnetic properties of oxide magnets of this invention;

FIG. 2 shows curves of magnetic properties of oxide magnets wherein CaO only has been added;

FIG. 3 shows curves of magnetic properties of oxide magnets in which Si0 only has been added;

FIG. 5 shows curves of (BH) of oxide magnets BaO.nFe O where n is between 5 and 6, containing in addition both SiO and CaO; and

FIG. 6 shows curves of H of the same magnets given in FIG. 5.

Briefly stated, according to the present invention, an novel composition of oxide magnet materials with specific compositional ratios is obtained, so that the magnetic properties of the magnet are considerably improved. The method of producing it, however, is not substantially different from that of the prior art, and as such it does not constitute part of the invention.

The following is an example of the magnet of the invention:

A mixture of metallic oxides in the molar proportions 5.3 Fe O and 1.0 BaO is intimately mixed, presintered and crushed, and then the crushed mixture of materials is combined with about 0.1% by weight of CaO and about 0.4 to about 0.8% by weight of S10 and sintered at about 1200 C. The resulting sintered oxides have the following magnetic properties:

r. CC

FIG. 1 gives the curves illustrating the abovementioned characteristics.

For purpose of comparison, either CaO or Si0 alone is added to the BaO mixture of (Fe O )=5.3. These mixtures were also sintered at 1200 C. In these cases, the vanation of the properties of magnets as a function of the proportion of CaO or Si0 is as follows:

Ca0(wt. percent) 0 0.05 0.1 0.2 0. 35 1 0 Br (gauss) 1,890 1,920 2, 04.0 2, 040 2, 020 ,000 H. (08.) 1, 840 1,89 1,9 1,990 1,970 1,800 (BH)..... 0. 87 0.91 1.00 1.01 0.99 0.9

Si02(wt. percent) 0 0. 2 0. 4 0. 7 1. 0 2. 0

2, 170 2, 2,140 2,060 2, 130 2, 100 2, 040 2, 010 (BH).....-- 0. 87 1.15 1.15 1.12 1. 09 1. 04 CaO(Wt. percent) 0 0. 05 0.1 0.2 0. 35 1. 0

FIGS. 2 and 3 show the curves illustrating the abovementioned characteristics.

It is clear from the above comparative tables that the magnetic properties of the material (=BaO.nFe O mixed together with both CaO and S10 are far better than those of the material mixed with only one of either CaO 01' S102.

The variation of the magnetic properties of the material as a function of the proportions of CaO and SiO may be given as follows (wherein the fundamental composition is BaO.(Fe O )5.3):

(molarratlo) 0.2/0.5 035/035 0.5/0.2 0.6/0.1 0.05/005 0.7/0

Br (gauss) 2,020 2,200 2,280 2,250 2,230 2,130 H. e. 1,950 2,040 2,180 2,160 2,110 2,100 1311).... 0.98 1.12 1.25 1.23 1.17 1.12

BaO(Fe O )n where n is between 5.0 and 6.0, containing 0.6 weight percent of Si0 and 0.1 weight percent of CaO are as follows:

Ratio of FezOs to BaO 5.0 5.3 5. 6 6.0

(0.) Nothing being added:

B 1, 910 1, 890 1, 710 1, 520 H 1, 940 1, 840 1, 750 1, 500 HLMX 0 89 0.87 0.75 0.57

(b) 0.6 wt. percent of SiOz and 0.1 wt.

percent oi 0210 being added:

Br 2, 260 2, 220 1, 980 H 2, 180 2, 2, 080 (BlEDmnunv 1.23 1. 16 1. 02

The curve A, of FIG. 5 shows the Br of the material containing 0.6% by weight of Si0 and 0.1% by weight of CaO, while the curve B1 shows the B1" of the material containing neither S10 nor CaO.

In FIG. 6, the curves A and B show the H, of the materials containing both, and containing neither, respectively, 'Si0 and C910.

Curves C and D of FIG. 5 show the magnetic energy (BI-I) of the materials with the same above-mentioned compositions.

3 It is clear from FIGS. 5 and 6 that the addition of (3210 and SiO is very effetcive for the improvement of the magnetic properties of the oxide material BaO (Fe203 ll As it can be readily understood from the foregoing description, the magnetic properties 05 the oxide magnet composed of Fe O and BaO, the ratio of Fe O to BaO being between 5.0 and 6.0, are much improved by the addition of 0.05 to 0.3% by weight of CaO and 0.4 to 0.65% by Weight of SiO the result being a magnet having a large coercive force and a high magnetic remanence.

The proportions of the oxides, when limited to the above-mentioned ranges give the maximum values of Br, H and (BH) within said range.

What we claim as new and wish to secure by Letters Patent of the United States is:

1. A barium ferrite magnet in which B210 and Fe O are in a molar ratio of BaO to Fe O of between 1:5 and 4 1:6 and wherein there are present from about 0.05 to about 0.3% by weight of CaO and from about 0.4 to about 0.65% by weight of SiO References Cited UNITED STATES PATENTS TOBIAS E. LEVOW, Primary Examiner J. COOPER, Assistant Examiner US. Cl. X.R. 25262.63 

